Screw-driving tool



Patented Mar. 20, 1945 -UNITED STATES PATENT o Fries" scam-Dame 'root James Richard Hawkins, Flushing, N. Y., assignor to Aircraft Screw Products Company, Inc., Y., a corporation of New Long Island Gity, N. York Application November s, 1943, serial No. 508,170 19 Claims. (Cil 10Q-1) The present invention relates to a tool for driving a screw-threadedelement into a boss member. Itis anobject of the invention to provide a tool suitable for I power drive whereby the screwthreaded element can be screwed a .predetermined length into the boss and wherein the driving torque is automatically stopped when the `element has reached a predetermined depth in the Fig. 8 is a cross-section along line =Il--B o f Fig. '1.

Referring now to the drawings. Figs. l andi?4 illustrate a tool according to the invention for driving a Wire coil screw thread a predetermined distanceinto the internal threading of a boss4 member. The tool in general denotedby I is boss. Another object of the invention is the provision of a tool @of the mentioned type wherein A the depth to which an element can be driven is adjustable within limits; The tool is in particular intended for inserting wire coil threadings of the type described, e. g. in U. S. Patent No. 2,150,876, and for this purpose, itlis furthermore contemf plated to provide for a combination of the tool shown as an attachment to a prime mover 2 which is not a part of the invention and, therefore. diagrammatically illustrated in dash lines, .but it is, of course, immaterial whether the design Y provides for a permanent or a releasable connecto said shaft and provided with an end for engageme'nt of the element to be driven, and connecting means between the' shaft andthe driver which means are operative onlyy in positions of the driver between an inner retracted position and another position in which ythe driver is spaced a predetermined distance from said end position.

Further details and objects of the invention will be apparent from the description given hereinafter and the accompanying drawings illustrat y ing several embodiments of the invention by way of example. In the drawings,

Fig. i is a longitudinal section of ing to the invention; 4

Fig. 2 is a side elevation of the same tool in another position of the driventhe right-hand half a ltool accordof the ligure being in section;

Fig. 2a is a longitudinal cross-section of a' modifled part of the Stool of F'igs.` 1 and 2;

Fig. 3 is a longitudinal section of another embodiment;

Fig. Vi is a section along line 4-4 of Fig. 3; Fig. 5 is aside elevation of a detail of the tool of Fig. 3; I

tion of the tool and the prirne mover. 'I'he'prime mover may be of any suitable or conventional type, as for instance an electric motor 'of thekind used in electric drills. 4There is indicated, furthermore. a rotarypart such as a shaft 3 and an externally screw-threaded, stationary part 4` oi' the prime mover 2.' The tool I in the embodi-` ment of Figs. 1 and 2 comprises a shaft 5 having a rearward end 8 so shaped that it may be coupled to the rotary part 3, e; g. by means of splines 1,

and a flange-like projection 8 serving to hold the shaft in a fixed axial position as it will b described hereinafter. Shaft 5 is provided with an axial bore 9 extending from its front face I0 close to the rear end 8.4 Interiorly of shaft 5, a

rod or driver II is axlallymovable. Its front end I2 is so shaped that it'can properly engage a screw-threaded elementior which the tool is destined, i. e. in the illustrated embodiment a wire coil I3 with a tang i6. Accordingly the driver end Fig. 6 is aflongi-tudinal section of a modified driver end and front end parts of the tool;

. Fig. '1 is alongltudinal section cfa third embodiment of the inventlon; and

is slotted at Il to receive therein the tang I4 and is formed of al cylindrical portion I8 of a diameter similar to the inner diameter of the coil I3.

Means are provided to couple shaft 5 and driver rod Il forl common rotation in any position of the driver between an innermost positionand a position at a predetermined distance therefrom. In.

the illustrated embodiment such means consist in a spline-and-groove connection in that shaft lis provided with a groove I1 extending from the front face IIl a suitably selected distance to the rear, and a pin I8 is secured in driver rod Il so as to project radially therefrom and to be capable of engaging said, groove I1 in the manner of aspline. It is, of course, possible in this connection to provide a plurality of splines and grooves rather than only one pin I8 and groove Il. The

innermost position of the driver can be predeter' mined in various manners, lfor instance by pin I8 abutting against the end wall I8 of groove Il, or by the driver end reaching the bottom of the bore tif the groove I1 is made longer than shown in Fig. 1. The driver can-.be shifted only to its 2 end position when the pin is in engagement with the groove I1. As long as pin I8 engages groove I1 shaft 5 and driver II are coupled for common rotation. On the other hand, no torque will be transmitted from the shaft 5 to driver rod II when the latter is shifted far enough forward for pin I8 to clear the end face I0 of` shaft 5.

An abutment beingV a portion of a stationary part of theftool is provided near itslower or front end in order to pla'ce the tool in correct position in relation to a boss into which a screw-threaded element is to be driven. In the illustrated formv of Figs. 1 and 2 this abutment is constituted by the front face of a sleeve-like casing of the shaft and the driver. The casing or sleeve 28 comprises three tubular portions of different diameter. The rear portion 2i forms a socket interiorly threaded at 22 so that the sleeve 20 can be screwed on the portion 6 of the stationary structure of the prime mover 2, to hold, between an inner shoulder 23 and portion 4, the aforementioned flange 8 of shaft 5, thereby preventing the. latter from shifting in an axial direction. However, the connection should be such that the flange 8 can freely rotate between said shoulder and said prime mover. A second portion 24 of sleeve 20 forward of the socket 2l has an inner surface 25 serving as va bearing for shaft 5. This surface extends a distance forward of the shaft 5 so as to form an annular space 28 in which pin -I8 can freely move if rod II is shifted sumciently far forward. The front portion 21 of sleeve 20 has an inner diameter smaller than surface 25. The so formed shoulder 28 when contacted by pin I8 prevents the driver rod Ii from dropping out of the assembly when its axis is in a vertical position. For apurpose to be explained later on, it is advisable to make the annular space asvaeaa prime mover may be started. whereupon the driver will rotate the wire coil I3 owing to the pin 'I8 engaging groove I1.y In consequence, the coil will enter the threading of the hole '35, and the driver will follow the axial component of the advancing coil owing to its weight while pin IS travels along groove I1. As soon as the pin I8 has arrived in front of face I of shaft 5,'the connection between shaft and driver will be interrupted so that the driver comes to a standstill j whereas the shaft may continue to rotate. (This is the position shown in Fig. 2.) The tool vmay now be withdrawn, leaving the coil I3 in the desired position in hole 35, the depth to which the coil is inserted being predetermined by the active length of the groove I1.

In certain instances it is desired to remove the tang I4 of the wire coil after the latter has been inserted. For this purpose, the projection or pin 48 has been provided and may be used in the following manner: The 'tool will be with drawn from the work 34 only so far that pin I8 bears on shoulder 28 while slot I5 of the driver 26 longer than the dimension of pin I8 in axial direction and to provide near the shoulder 28 an inner projection which the pin I8 may engage when it has left groove I1. In the embodiment of Fig. 1 such projection'is constituted by a. pin

48 secured to the wall of sleeve portion 24. The upper partof the portion 21 may have an inner surface 28 serving to guide the driver in coaxial alignment with shaft 5, whereas the inner surface 30 of the lower part of portion 21 is spaced from the driver end I8 suiliciently to receive the wire coil element I 3 in the annular space 8| therebetween. Portion 21 has an end face 32 to serve as the mentioned abutment when the tool is placed on the top surface 33 of a boss or work member 34 with a threaded hole 35 to be lined with an insert with the aid of the tool.- 'The face 32 is so spacedfrom the abutment of the I8 so that the tang I4 engages the slot i5 and the coil body is located in the annular space 3l.,

fThen, while the driver is in its rearmost position 'in which pin I8 abuts against the end wall I8 of the shaft groove I1, the front t'p ofthe driver may be inserted in the threaded `hole 35 of the boss 34 and the face 32 held downward against the boss surface 33; face 32 being atright `angles to the tool axis facilitates co-axial alignment of the wire coil I3 with the hole 35. Then. the

willbreak or shear oi! the tang in the 'manner more fully described in U. B. Patent No. 2,210,061. It will be apparent that the tool according to the `invention is ,extremely simple since it mainly consists of only three parts, viz. the shaft, the Ydriver and the stationary member embodying the bearings and guiding elements for. shaft and driver, and the abutment for engagement with the boss into which the screw-threaded element is to be driven. f

It has beenstated hereinbefore. that the driver during operation will advance in axial direction owing to its weight. This is true, if the tool is applied to the work downward with the driver axis vertical or approximately vertical. However, it has been found that even if thev tool is used with the driver axis in a horizontal position. no additional means are requiredto advance the driver in axial direction. Apparently, the friction set up `between the coil tang I4 and the flanks of the end slot I5 is suilcient in most instances to cause the driver to follow the wire. coil when the latter enters the threading of hole 35 owing t0 the rotation. The fact that the tool may be Vused and is useful in directions where the advancement of the driver is due to the mentioned friction rather than to gravity renders it advisable to provide for a predetermined inner end position of the driver as defined by the abutment of pin against groove wall I9. Where gravity tends to advance the driver. the correct inner end position is insured without additional means by the screw element IS resting on the top convolution of the threading of hole v3Ii when face 32bears on face 33 prior to the starting ofthe drive. Where, however. no force starting, the driver must be so held by means such prevails to shift the driver forward prior to the as the mentioned abutment that the front end of the screw element projects suiilciently. from face 32 to engage the threading of the'hole 35 immediately when 'the drivergisstarted to rotate. If it is intended to use the, tool in positions where the driver will not readily follow'the screw elementadvancing 'owing to itsbeing screwed into a threaded hole, it may be advisable to add a soft spring of sufficient strength to counterbalance the weight of the driver. An example of such struc-4 shaped screw elements. In fact, this embodiment 4 of the invention isintended for the use with mainly one type of screw elements, namely, with tang-provided wire coils within the limits of a certain maximum outer and a certain maximum inner diameter. With any such wire coil, regardless of its length, the depth -to which itvwill be inserted by the tool is predetermined by the length of the groove I1: or, in other words, by the distance the driver can shift in axial `direction from its position when the screw element bears on the top convolution of the threading of the hole into which it isto be inserted, to that position in which the driver is disengaged lfrom its connection with the hollow shaft. lNow, in many instances, it is desirable that a tool according to the invention is applicable to a greater variety of screw elements. For 1this purpose, parts of the tool may be rendered adjustable and/or exchangeableto "adapt the tool to particular requirements. Such a tool is illustrated in Fig. 3.

In this embodiment, the hollow shaft is very similar in structure to the shaft 5 of Fig. 1.` It is provided with a' splined end |08 for connectionl to a shaft of a, prime mover (not shown), a flange |08, an axial bore' |03,'an end face ||0 and a longitudinal groove ||1. Interiorly of the shaft but projecting therefrom the driver rod III is ar-` ranged with a spline or pin |`|3 adapted to engage the groove II1. The upper end of driver I Il is provided .with an axial threaded bore ||2 into which a bolt |I3 is screwed so that `the head II4` constitutes an axially adjustable abutment of the driveragainst thebottom I I5 of theshaft bore'l03. d The lower end portion of the driver is formed as a separate piece IIB releasably attached to the driver rod y| II-,so that it may beexchanged .for another piece according to the nature and shape of the screw element'to be inserted in each particular case. For this purpose, the lower end of the driver rod I is also provided with an axial threaded bore H3, and the piece IIB comprises an upper threaded extension fitting the threading of bore H9, and acollar-like portion |2|.with a radial bore |22 for the application of a tool for turning the piece I I6 in relation to `the driver rod I||. Thelower end of piece ||3 is slotted at |23 similarly to and for the same purpose as the slottedend I2 .of 'the driver of Figs. 1 and 2. It will be clear that the described structure does not only permit the piece I I 5 to be exchanged but valso to be adjusted within limits so that the slot |23 may be spaced desiredA distances from the head ||4 and from'. the pin H3. A gap occurring beis encased in 1l and 2, for attachment to a stationary structure of the mentioned prime mover. Contrary,

however, to the sleeve 20 ofthe first embodiment, sleeve |25 does not directly embody an end face to bear on the work during the 'operation of the tool. A separate shoe piece |21 is provided for this purpose. For this reason, the sleeve |25 except for its socket portion may have a straight bore vthroughout its length according to'vthe diameter of the shaft |05. 'I'he mentioned shoe piece `is a means toprovide for adiustability of the end face or abutment of the tool and also to re,-

.ceive therein the screw element which is intended to be driven by the tool. The shoe piece will have'to be shaped accor-ding to thescrew element for whichit is destined, and. therefore,

. m'ust be exchangeable in order to make the tool applicable for a varietyof differently shaped screw elements. In the event it is desired to use the tool for,inserting a wire coil in a threaded hole 'as described in connection with the embodiment of Figs. 1 and 2, it has been found desirable to prevvindl the wire coil, i. e. to contract it before it is screwed into the threading of the work. An eiiicacious device for that purpose has been disclosed in U. S. Patent No. 2,316,221, and

may be readily combined with the tool according4 to thepresent invention by shaping .the lower end portion of the sleeve in Fig. 1 or of a separate shoe piece of the kind just mentioned so as to cooperate with the driver'in the manner of the cited patent.

Such-a structure' has been shown in Fig. 3 as it will be apparent from the following description of the shoe piece |21. This shoe piece is a substantially tubular member telescopically inserted in the lower portion of the sleeve |25. It is .pro`

vided with a longitudinal groove |20 engaged by a pin |29 which-.is secured to the wall of sleeve' |25 and projects inwardly therefrom. This pin prevents the shoe -piece from dropping out of sleeve |25; the groove'on the other hand is sumciently long to permit shifting ofthe shoe piece a required distancel in an axial direction. The lower end of the groove |20 is so located that lin the topmost position of the shoe piece a sumciently long annular space |30 remains free between the rear face |3| of lthe shoe piece and the front face ||0 of the shaft |05 for the spline or i pin ||8 to move freely therein when it is disengaged from the groove I |1 of shaft |05. The shoe y piece is further provided with a recess |32 in its jectsfrom sleeve |25 is providedwith an external rear end to receive therein the pin ||8 when the 'driver is suiiiciently far projected. Since the shoe poseof coupling the driver to the sleeve |25 when the tang of an inserted wire coil shall be broken off after insertion as4 it has' been described hereinbefore. A portion of the shoe piece |21 which prothreading |33engaged Iby a nut |34 which may abut against the-front face` |35 of the sleeve |25.. 4A set screw |33'may be provided to secure the nut |34 in an adjusted position. Nut |34 serves to adjust the spacing of the end face |31 of the shoe Y piece from the front face I|0 of shaft |05 so that "the face I3'I`can constitute an adjustable abutment for the same purpose as that described with respect to the front face of the tool of Figs. land 4 I s 2. The lower part oi the shoe piece |21 is laterally recessed at |38 and the recess is so dimensioned that a screw element I3 to be inserted with the aidof the tool may be placed inside of the the tool. For adjusting the tool it is recommended rst to set screw |I3 so that the driver'rod can shift from the position where the screw head ||4 abuts the bottom ||5 of the shaft |05 to the position ywhere the p in IIB is clear of the groove 55 the gap between its collar |22 and the end-of the 55 driver-.is to bevlledwith spacers. until the tip oi' the end IB lslightly'px'oiects into the hole of the prewinder .threadinsidL .11'. however. the tip 'of the piece ||I projects too Iarinto they threading `-|4| .while the shoe Die@ |21is'in its V'm backward endtpositiontnut |84 aliuttiris .against-s.; face Ilsisto beturned toshift the piece- |21 iorward until the desired relative positionof the tip o! the piece IIS and face |42 is reached. Wielen this has-been done. theshoepiece is to be 'puliled forward in order to be sure that in its forward end position in which the pin |28 contacts the backward en'd of the groove |28-, the recess |38 is free of the end piece IIB. Otherwise the total shoe piece to bear against the remaining wall por- 5 length of the driver assembly must be Vshortened Y tion |88 (Fig. 4), and on the top or the annular by screwing the end piece IIB backward into end portion |40 of the shoe piece. In order to driver rod ||I after sumcient spacers' |24 have place screw element I3 into the recess it is, of been removed, and the inner end position oi' the course, necessary viirst to project the piece |21 shoe piece |21 must be readjusted with the aid suiilciently far so that the end I|0lof the driver 10* of 'nut |34. has cleared the recess. The annular portion |40. .When correctadjustment is accomplished the is' interiorly threaded at |4| according to the shoe piece |21 is to be pulled forwardto clear the shapeand pitch of the screw element I3 and acrecess |38 so that wire coil I 3 may be inserted cording to the diameter the screw element I3 vis in the-recess |88 with its front convolution bearintended 'to have immediately prior to its inser- 15 ing on the face |42. Then the shoe piece is tion into thehole for which it is destined.. This. shifted back until the nut |34 abuts against face threaded annular portion in combination with |35. Thereby the driver end passes axially 'the driver end constitutes the aforementioned through the wire coll so as to engage with its y prewinder. The application of such prewinder is slot |23 the tang I4 ot the coil. -The tool may desirable because in many instances the wire 20 now be brought into position in relation to a .coils here under consideration are originally tapped hole into which the wire coil is to be wound with a diameter slightly larger than that inserted and the prime mover may be started. of the tapped hole for which they are destined. Rotation of the Prime mover causes Shaft |05 t0 Now, in lconnection with such prewinders I have take the driver along which thus willrotate the found that it is extremely dimeum te cause the 25A wire ceu thereby screwing the coil iirst through first convolution of a wire coil to enter ,the the prewinder and then into the hole of the work. threading |4| if the top face |42 of the annular rAs `heretofore described, the driver will follow portion |40 is at right angles to the axis of the the axial movement of the advancing wire coil tool. This dilculty can be avoided if the face 4until the pin- |8 is free of face ||0 and'comes to on which the wire coil comes to bear before it is: 30 a standstill within the annular Space Y |30- In caused to enter the threading lei is more or less order to remove the tens of the coil the tool may parallel tothe helical line of the first coil convolu` be so far. withdrawn from the work that the pin tion. It this is done, as it has been shown in H8 can drop into the recess |32 whereupon the Fig. 5. the top convolution ot the threading I4| tang can be broken Off by turning the tool in the ends with a more or less complete cross-section direction opposite to that in Which the coil. had |43 of a convolution rather than *with` a taper been Screwed home. When the tool is then rewhich would .be formed if the top face intersects moved from the work and the driver shifted bacia the helical end convolution at right angles to. -into its innermost position the tool ileady t0 y the exis of the threading. If the top fece |42 is 40 receive another wire coil for insertionshapedin the stated manner, awire coil hearing It has been stated hereinbei'ore, that the tool thereon will be coaxially aligned with the threadaccording to the invention is useful for screw eleing |4I and the front end of the coil will easily ments of a character also other than wire'ooils. drop behind the convolution end H8 of the This has been exemplied in Fig. 6 showing the threading to engage thefirst groove thereof. lower Portion of thetool of F18. 3 adapted for The tool according to the invention may be application to a screw stud |60. In this event a used in the following manner. Screws IIS.` |28 driver end Pieee H9' embodying e Screw driver and nut |34 are adjusted according to the depth n blade I8| is substituted ior the end piece-I It of to which thev wire coil- I3 is intended to he in- Fis. 3 and screwed with a threaded upper end serted in a boss or nut member with the aid of 5o |62 into the threaded bore IIe of the driver red Similarly. another tubular shoe piece |21' is substituted for the piece |2l and inserted in sleeve |25. By shifting the shoe piece in an axial direction, its end face |81' can be adjusted in relation to the other parts of the tool and the set screw |29' in place of the pin |29 can be used to secure the shoe piece |21' in its adjusted poms tion. The lower portion |6 of the shoe piece is interiorly' so formed that it serves to ,hold and o guide the screw stud |00 during its being inserted in a boss to a predetermined depth. All other parts of the tool may be according to those shown in Fig. 3 so that no further explanation of the operation of the modiiication of Fis. 8 is required.

Whereas in the preceding embodiments 'of the invention, the relative location of the end face (I0 in Fig. ll and |I0 in Fig. 3) of the hollow shaft'is determinative for the depthto which a screwl element will be inserted with the aid ,of the tool, it is similarly possible to render an kend face oi the driver capable oi accomplishing that function. An example o! such a structure .s AYis illustrated in Fig. 'lv-in whichalsora modincaf Y Vtion ofthe adjustment means and 'a certain de` tent enthas been shown.; In Flai?. the r,4

sleeve member 228 forms the bearing lfor the hollow shaft 205 into which the driver rod 2|| lengages with its rear end portion 28| substantially in the manner of Fig. 3. However, in` this case, portion 280 is provided with 9, groove 2|.1

and shaft 205 with inner spline projection 2|0 capable of engaging the groove. A portion 28| forward of the portion 280 of rod 2|I is exter-V t nally screw-threaded andsl nut 262, preferably of selfdockingquality, is adjustable on that threading. Thus. the nut when bearing against the iront face 2|0 of shaft 205 dennes the innermost end position of vthe driver in a manner similar to that of the screw head ||4 abut ting against the bottom |I5 of the hollow shaft |05 in Fig. 3. Y

On the other hand, the driverY rod 2|| may! be shifted forward with the nut 282 moving in the annular space 238 until the rear face 283 of the rod is forward of -pin 2|8 so that the nellal o shaft. may-'be accomplishedwithout requiring the tool to be -partly disassembled as is the'case in the tool of Fig. 3. Means may be provided to avoid this .inconveniency In the embodiment of Fig. 7, such means consist of a`groove or plurality of grooves 218V in the periphery of nut 282,` in conjunction with an inner projec-4 tion /such as pin 211 near the lower end of the space 2062 `Now it will be clear that in order to accomplish` an adjustment it is only necessary after the detent 26s has been withdrawn, te

A drop the driver and to bring pin 211 into enshaft and driver become disconnected. Forward 'movement of the rod 2|| may be assisted or caused by a spring 242 in a cylindrical recess gagement with a .groove 218 whereupon the front end of the driver may be 'grasped and turned to alter." theV position of the nut 282 thereon.- when, then, the driver` 1s returned tous re.

tractedposition the tool will' be ready for'operation. 4

It will be understood that various changes and modifications in-the specific form of the vtool may be made without departing from the splrit and essence of 4my invention which is not llm- 24| of the shaft 205. y'I'he one end of the spring ited by the particular'disclosure of the embodiments thereof illustrated and described butby the scope of the' appended claims. I claim:

1. In a tool of the'type described. thecombina-- .tion of a shaft hollow through at leasta portion of its length,a driver member having a front end shaped for engagement of a` screw-threaded element to be driven by said tool and having a rear end portion adapted to move axially within said |40 of the shoe piece |21. Thus, the'function as .l of thetool of Fig. 7 is the same as described with respect to the tools of Figs. 1 and 3.

In certain instances it may be found inconvenient `that the driver can freely move in axial direction while the tool is not in use. For this reason a, releasable detent may be applied to holdthe driver in retracted position. An exam-l ple of such structure is shown in Fig. 7, where against the front face 2|0 of the shaft 205.` A pin 266 is secured to the outwardly projecting end of the detent and is engaged by the forked .end 281 of theone arm 280 of a lever pivoted at 259 on the outside of the sleeve 225. A spring 210 engaging the other lever arm 21| tends to 'hold the end 201 against the faceof the wart 284 with the detent in operative position. By pressing lever arm 21| towards sleeve 225 the the sleeve 225 is provided with awart 264 through 4which a detent 285 projects into the space 238 in front of the nut 252 when the latter bears shaft, said shaft and said driver member includingmeans for a disengageable spline and groove connection of said shaft and driver, the effective length of said means inl axial'direction being approximately equal to the desired depth to which said screw-threaded element is to be driven in a job, and stationary sleeve-like means consti-4 tuting a bearing forV said shaft and a guide for the driver in axial direction. the front face of said sleeve-like means constituting an abutment to engage' said job during the driving operation, and said driver member being of such lengththat disengagement of said spline and groove connection will occur while the driver front end is still in engagement with-the screwethreaded element driven to the desired depth. e L y 2. A tool as claimed in claim l, said sleeve-like member and said shaft including 'abutment means y `to prevent said shaft from axial movement in the L direction rof the front end of the tool.

I detent will be removed so that theV driver may become'free t-o shift in axial direction. `It is.

of course, possible and may be desirable that withdrawal of the detent occurs simultaneously or in timed relation to the starting of the prime mover.

Means for this .purpose 'may be pro- 3, A tool as claimed in claim 1 further comprising means to connectsaid shaft to a prime mover, a detent to retain said driver in its retracted position, operative means in engagement with said detent and pivoted on said stationary member for withdrawing said detent'from retaining position vided in connection with the lever arrangement i 268 to 21| and an example-of suchv meansis diagrammatically indicated by two-contacts 212 and 213 insulatedly-secured to lever arm 21| and sleeve 225 respectively, and connected to electricl leads 214 and 215 which in turn may be conf nected to a starting device (not shown). Thus, if lever 21| is actuated a current may be -closed through vthe contacts 212 and' 213 at -the same time when the detent 205 is withdrawn.

and switching means in connection with said operative means and' adapted to be connected `to said prime mover to start the latter.

' 4. Atool as claimed'in claim 1, wherein the iront end portion of said sleeve is so shaped as to Where frequent changes of the adjustment of the tool are-necessary, it may be desirable that `the adjustment of the distance which the driver is axially shiftable while connected to the hollow receive therein said screw-threaded element and to hold it in a position for engagement by said driver member prior tothe start of the driving t operation..

l5. In a tool of the type described the combina.

tion of a shaft hollow through atleast a portion 'of its length, said shaft being provided with an interior groove extending lengthwise from its front face, a driver member having a front end shaped for engagement of a screw-threaded element to be driven by' said tool and having a rear end portion `axiallymovable within said shaft, a

d tion of a. rotatable hollow shaft member. adriver groove of saidfshaft, and a stationary sleeve-like member in telescopic relationships said shan and having its' front-end projecting from said shaft and shaped for engagement of an extramember constituting a bearing for said shaft. the l front face of said sleeve-like member constituting an abutment to engage a job into which said screw-threaded element is intended to be driven,

and said driver'member being of such length that its front end projects from said front face of said sleeve-like member the distance required to' drive said Yscrew-threaded element vto the desired depth in said job before said spline-like projection is disengaged from said groove of said shaft. 6. In a tool of the type described the combination of a shaft hollow through at least a portion of its length, said shaft having an interior splinelike projection short-in thelongitudinal direction. a driver member having a frontend shaped for neous screw-threaded element to be driven by ,said tool, interengageable meansA of said shaft and saidl driver to insure common rotation of said members, said means being of such an extension in axialdirectionasto be operative in positions of the driverbetween an inner retracted position thereof anda position in which said driver is projected a predetermineddistance from said retracted position and in which said means are disengaged, and a two-part'member stationary in relation to said shaft and said driver during their rotation. one part of said two-part member 'embodying a bearing for said shaft. the other part having a front end face at engagement of a, screw-threaded element to be driven by said tool and. having arear end portion axially movable within said shaft, the rear end portion of said driver being providedV with a iongitudinal groove adapted forl engagement with said projection of said shaft', and a 'stationary'v sleeve-like member constituting a bearing for said right angles to the'axis-of said bearing and being adjustable in relation to the other part in the direction of said axis.

1G. In a tool of the type described the combination of a rotatable hollow shaft member, a driver and said driver to insure common rotation of said' quired to drive said screw-threaded element yto the` ldesired depth in said job before ,said spline-like projection is disengaged from said driver member.

7. In a' tool oi the type described the combination ofa rotatable hollow shaft member, a ver member in telescopic .relationship to said shaft and having itsfront end projecting from said shaft and shaped for engagement of an extraneous screw-threaded element to be driven by said groove of said tool, a spline-and-groove connection of said t and said driver,`said spline and groove being of such extensions in the axial direction as to be operative in positions of the driver between its re-- tracted end position and a position in which said driver is projected a predetermined distance from said retracted position and in which said spline and groove. are disengaged, and a stationary 'sleeve member constituting -a bearing for said I a front end portlonprojectable from the frontv member in telescopic relationship to f said shaft and having its front end projecting from said shaft and shaped for engagement of an extraneous screw-threaded element to be driven by' said tool, interengageabie means of said shaft members between two axially spaced positions of said .driver member, a stationary sleeve embodyings. bearing for said shaft, and a substantially tubular shoe piece in telescopic lrelation to the front end portion of said sleeve and exchangeablyy attached thereto, said shoe piece having a front end face at right angles to its axis and being interiorly shaped. so as -to receive therein said screw-threaded element prior to its being driven by saidV tool.

11. Ina tool of the type describedV a hollow rotatable shaft'. a driver including a rear rodlike part in telescopic relationship to said shaft, and a front part coaxially and exchangeably connected to said rear part and adjustable to vary the total driver length. the front end .of said front part being shaped for engagement of an extraneous screw-threaded element to be driven by said tool. interengageable means of said shaft and'said rear driver part to insure common rotation of said shaft and said driver between .two-

, including a front face at right angles to the bearend of said sleeve and shaped for engagement. Y,

of an extraneous screw-threaded element, said driver being axially movable between s. rear end position and a front end position 'andfhavins a and said' ver to insure common rotation of said them for commonv rotation in all positions vof v'the drivery between said rear end positionland said f end position from rotating relatively to 'said sleeve.

s. m a reci of the type described, the eombmami hetwemftwo axially vspaced positionsv of said driver member. a PGrtion of said driver screvv-threatleti.V a screw-threadedmemberin en'- ement with the'threading of said driver -portion, said screw-threaded member constitutingv m adjustable abutment of said driver'against aface' 1 of saldshaft for adiustment ofthe spacing of 1 said twol driver positions. and la. stationary memoluding frontiace at right angles to the'bearing a .hearing for said shaft and interiorly screw-threaded,

said screw-threaded element is intended -to be driven.

13. A tool as claimed in A rear end portion of said driver memberls insaid screw-threaded member being a headed screw bolt in engage ment with said inner threading, and said hollow shaft has a bottom against which the head of said bolt can abut.

14. A tool as claimed in claim 12 wherein said threading of said driver is an outer threading, said screw-threaded mexnber'being` a nut on said threading and having a rear face to abut against the iront face of said shaft.

15. A tool as claimed in claim'izfurther comprising second interengageable means in connecclaim 12 wherein the 7 coil to be inserted Vby the tooluinto a tapped hole, said driver being axially movable between a rear end position and a iront end position and having a critical intermediate position, interengageable means oi' said driver and said shaft to couple them for common rotationin all positions of tion with said screw-threaded'member vand said stationary member to prevent the former from turning relatively to the latter, said second means being so located and arranged that they may be caused to interengage when said driver member is protracted beyond a position in which the m'st mentioned interengageable' means are ,disengazed. 1

16. In a tool oi the type described the combination oia rotatable hollow shaft member. a driver member in telescopic relationship to. said shaft/and having its front end projecting from said shai't and shaped for engagement of the tang of an extraneous tang-provided wire coil to beA i tion and in which said means are disengaged, and

a two-part member stationary in relation to said shaft and'said driver during their operation, the first part of said stationary member embodying a bearing vfor said shaft, and said second part embodying in ccoperati'onwith said driver a prewinder to contract said wire coil prior to its insertion in said hole.

17. In a tool ofthe type describeda stationary sleeve, a hollow shaft rotatable, in the rear portion of said sleeve, a -driver having a rear end portion Atelescopically arranged within said shaft and a front end portion shaped for enswement ci the tang of ,an extranecnis tansprovided wire the driver between said rear end position and said critical position, a substantially tubular shoe .piece axiallyshiftable with its rear portion between two end positions in telescopical relationship to the front end portion of said sleeve and being secured thereto against rotation, a portion of. said shoe piece projecting from said sleeve beingdaterally recessed, to receive therein said I wire coil, and the shoe piece portion in front of said recessbeing interiorly screw-threaded with a diameter to which it is desired to contract said wire coil prior to its insertion in said tapped hole. the dimensions of said driver and'- said shoe piece being such that with both in their respective end positions the front end portion ofthe driver pro- Y jects through the recessed portion of said shoe piece, and that with the driver in its rear and to'be screwed into a tapped hole, consisting of a slotted driver and ya substantially `tubular shoe vpiecein which saidfdriver is rotatable and axially shittable and wherein said tubular member is provided with a lateral recess in the rear ci an interiorly threaded iront portion,` said recess being so dimensioned as to receive therein said wire coil, and said interior threading .being substan- I tially according to the desired pitch and diameter of the prewound coil, that invention which con- J sists in, that the rear face of said interiorly threaded portion is substantially helicoidal according to the helical line of the front convolution of said coil, whereby said coil when bearing on said face will' be substantially coanially aligned with said driver and said interior thread- Jams aleman Hawms. 

